Regulation of synthesis of a hormone induced protein set - Glenn A. Galau, PI A coordinately regulated set of genes has been described which are highly regulated during the final development of many plant embryos. These are termed Late embryogenesis-abundant (Lea) sequences. We believe, but have not yet proved, that they are regulated primarily at the transcription level. Regulators include the plant hormone abscisic acid and probably events related to incipient dehydration prior to full desiccation of the mature seed. The characteristics of the structure and regulation of Lea genes suggest that the LEA polypeptides serve as desiccation protectants. Such a function is expected to be required by representatives of most groups of organisms. Consequently their study, in addition to providing basic information on concerted regulation of gene expression, may be important in understanding the mechanisms which allow reversible dehydration. The specific aims of the proposal are to: 1) Isolate and sequence both members of several digenic cotton (Gossypium hirsutum) Lea families which share homology with those in tobacco and Arabidopsis. 2) Characterize their transcription during normal embryogenesis and in excised embryos treated with abscisic acid, water stress, and agents which may be associated with dehydration. In vivo transcription and transcription in nuclear run-on systems will be examined. 3) Develop a cotton transient expression system using embryo protoplasts and electroporated reporter genes to determine the sequences in Lea genes which are responsible for the transcriptional regulation. 4) Transform normal and altered cotton Lea genes into tobacco, using Agrobacterium-based vector systems, to correlate the regulation of their expression during tobacco embryogenesis with their structure. 5) Isolate mutants of Arabidopsis defective in the ability of embryos to survive normal desiccation, but rescuable by precocious germination. These are predicted to be deficient in Lea function and as such should help elucidate both the regulation and function of these proteins.